With a rivet element, the element is inserted into a pre-pierced sheet metal part and riveted to the sheet metal part by beading over the rivet section of the fastener element. The fastener element itself has a fastener part, i.e. either an internal thread or a bolt shaft with an external thread, whereby a further component can be secured to the sheet metal part using a bolt or a nut respectively. Piercing and riveting elements are made self-piercing, i.e. the element itself cuts the hole in the sheet metal part and is subsequently riveted to the sheet metal part. With press-in elements the sheet metal part is again also pre-pierced and the element is then passed through the hole and pressed together with the sheet metal part so that sheet metal material flows into undercuts of the pressing element and locks the pressing element relative to the sheet metal part, so that it is firmly secured to the sheet metal part and cannot be straightforwardly pressed out of the sheet metal part.
Such fastener elements have, in the construction of motorcars, largely displaced welding elements which were previously welded to sheet metal body parts or the like. The welding on of elements is, on the one hand, difficult to integrate into the manufacture of individual components by mechanical deformation and also leads to an undesired contamination of the sheet metal part. Further, welding elements cannot be used with various sheet metal parts, for example when these are pre-painted or consist of two sheet metal layers, optionally with a plastic membrane disposed between them. They can also not be used when the sheet metal part is a high strength part, since the heat which is associating with the welding operation leads to an unacceptable reduction of the sheet metal properties in the region of the weld location. In the manufacture of sheet metal parts for motorcars large numbers of parts are required and the sheet metal thicknesses in question normally lie in the range from 0.6 mm to 2.5 mm sometimes beyond this to 3 mm or slightly more.
A fastener element in the form of a nut element is known from U.S. Pat. No. 5,251,370 which has a flange part of larger diameter and a shaft part of smaller diameter which extends away from the flange part and merges at its end remote from the flange part into a cylindrical rivet section the outer side of which lies approximately flush with the outer side of the shaft part, i.e. has the same diameter, with the side of the flange part adjacent the shaft part forming a sheet metal contact shoulder and with features providing security against rotation being provided at the shaft part and/or in the region of the sheet metal contact shoulder.
A fastener element of this kind is attached to the sheet metal part in accordance with the named US patent by means of the so-called clamping hole riveting process. For this purpose, the sheet metal part is pre-pierced and the region around the piercing is shaped into a conical projection or into a conical collar. During the passing of the rivet section of the element through the sheet metal part, which takes place from the side of the conical projection, the rivet section is beaded over and dilated and simultaneously the conical projection is at least partly reversed, whereby the hole of the conical projection is reduced in diameter. A type of strangle-hold takes place between the sheet metal part and the fastener element and serves for excellent mechanical properties of the connection between the fastener element and the sheet metal part. The conical projection of the sheet metal parts is made differently for different sheet metal thicknesses so that one can cover different sheet metal thicknesses with one element.
In the patent specification it is brought out that the element can be used with sheet metal thicknesses up to 4 mm and, as stated above, sheet metal thicknesses of greater than 3 mm are relatively rare in motorcar construction.
Rivet elements are also used in the manufacture of trucks, however on a much smaller scale. Essentially only the use of rivet elements from motorcar manufacture is known, which are also used in thin sheet metal parts of trucks, for example in the region of the driver's cabin. More stable sheet metal parts of trucks, i.e. with the sheet metal thicknesses greater than 3 mm and normally greater than 4 mm and larger are—if at all—only provided with rivet elements in the most rare cases, since the rivet elements that are available are not designed for such thick sheet metal parts. Furthermore, far fewer trucks are manufactured in comparison to motorcars. The methods used in truck manufacture lead to welding elements dominating there.